Liquid crystal displays (LCDs) continue to improve in cost and performance, becoming a preferred display type for many computer, instrumentation, and entertainment applications. Typical LCD mobile phones, notebooks, and monitors include a light guide plate for receiving light from a light source and redistributing the light more or less uniformly across the light guide plate. The light source, conventionally being a long, linear cold-cathode fluorescent lamp, has evolved to a plurality of discrete light sources such as light emitting diodes (LEDs). In a given size of an LCD, the number of LEDs has been steadily decreased to reduce cost. As a result, the pitch of LEDs becomes larger, which results in more noticeable hot spot problem (i.e., light near LEDs than between LEDs in the first few millimeters of the viewing area of the LCD). The hot spot problem occurs because light from discrete LEDs enters light guide plate non-uniformly, that is, more light is distributed near LEDs than between LEDs. Many light guide plates (LGPs) have been proposed to suppress the hot spot problem. Some LGPs have continuous grooves near their edge such as the ones disclosed in U.S. Pat. No. 7,097,341 (Tsai). Some LGPs have two sets of linear grooves of different pitches on their light output surface. Some LGPs have two or more sets of dots of different sizes. Other LGPs may combine grooves and dots of different sizes.
While the prior art light guide plates are capable of suppress the hot spot problem to a certain degree, they are still not satisfactory due to the complexity in the mass production of those LGPs. Thus, there remains a need for a light guide plate that can be easily made and is capable of suppressing the hot spot problem.